Why are grandsons and other descendants sometimes called "sons" in the Bible?

Yet we should quickly note that if one wants to enter into the details of the subject before us, one must be very guarded in his conclusions, for Jewish genealogies present innumerable difficulties. First, very frequently those who are called the son of so-and-so are not necessarily his children at all, but his grandsons, or even his grandnephews. Then there are cases where the head of a clan is regarded as the father of a generation, all the generations between being omitted. There are cases where through the “right of redemption” a distant relative (see the Book of Ruth) becomes the head of an extinct family. There are those cases, very frequent during the captivity, where one family took a place in the inheritance of another family which had disappeared, without being related by direct descent to the head of that race. There are cases too where, the name of ancestors being missing, the name of the birthplace replaced, so to say, the name of the family head. There are cases, common among the Jews, where a person had more than one name (see, for example, these well-known names: Benjamin and Benoni, Reuel and Jethro, Solomon and Jedidiah, etc.). And lastly there are cases where an abridged genealogy was given, the names indicated being nothing more than a few pointers to establish the line of descent.

Yet we should quickly note that if one wants to enter into the details of the subject before us, one must be very guarded in his conclusions, for Jewish genealogies present innumerable difficulties. First, very frequently those who are called the son of so-and-so are not necessarily his children at all, but his grandsons, or even his grandnephews. Then there are cases where the head of a clan is regarded as the father of a generation, all the generations between being omitted. There are cases where through the "right of redemption" a distant relative (see the Book of Ruth) becomes the head of an extinct family. There are those cases, very frequent during the captivity, where one family took a place in the inheritance of another family which had disappeared, without being related by direct descent to the head of that race. There are cases too where, the name of ancestors being missing, the name of the birthplace replaced, so to say, the name of the family head. There are cases, common among the Jews, where a person had more than one name (see, for example, these well-known names: Benjamin and Benoni, Reuel and Jethro, Solomon and Jedidiah, etc.). And lastly there are cases where an abridged genealogy was given, the names indicated being nothing more than a few pointers to establish the line of descent.

In Chronicles the accuracy of genealogies depends in large measure on the importance the Jews placed upon them during their captivity, and the disorder they reveal corresponds to the state of the Remnant as we find them in the books of Ezra and Nehemiah. Quite a number among the people and among the priesthood could not prove their genealogy. Though lacking heads, they could nonetheless be recognized by the names of their families, groups, and cities, which in this way became in essence a “moral person,” recognized as the stem of their ancestry (cf. Ezra 1 and here 1 Chron. 2:50, 54-55; 1 Chron. 4:4). In addition, the great disorder that came in explains, at least in part, why very distant descendants of the head of a clan were considered as his sons. (See for example, Shobal, the great-grandson of one of Judah's grandsons (cf. 1 Chron. 2:50; 1 Chron. 4:1). This same disorder also explains why we see a family head, whose name had not been previously mentioned, suddenly appearing and counted as the head of a clan (1 Chron. 8:33).

In Chronicles the accuracy of genealogies depends in large measure on the importance the Jews placed upon them during their captivity, and the disorder they reveal corresponds to the state of the Remnant as we find them in the books of Ezra and Nehemiah. Quite a number among the people and among the priesthood could not prove their genealogy. Though lacking heads, they could nonetheless be recognized by the names of their families, groups, and cities, which in this way became in essence a "moral person," recognized as the stem of their ancestry (cf. Ezra 1 and here 1 Chron. 2: 50, 54-55; 1 Chron. 4: 4). In addition, the great disorder that came in explains, at least in part, why very distant descendants of the head of a clan were considered as his sons. (See for example, Shobal, the great-grandson of one of Judah's grandsons (cf. 1 Chron. 2: 50; 1 Chron. 4: 1). This same disorder also explains why we see a family head, whose name had not been previously mentioned, suddenly appearing and counted as the head of a clan (1 Chron. 8: 33).

Mr. N. ought to know, if he writes on such a subject, that many learned men think that the genealogy in Luke is that of Mary pursued in the order of nature up to Nathan. I am well aware others have thought it that of Joseph also; and as Salathiel was son of Jechonias, and Zerubbabel his grandson through Pedaiah — so also he may have been collaterally, or by his mother or grandmother, descended from Nathan. If there were no brothers of such mother, he would rank as such. They have applied the same reasoning to Eli as regards Joseph. The truth is, in these Jewish genealogies, where grandsons are called sons — nephews and cousins, brothers — and children raised up to a man by a brother taking his widow, whose seed is called then after her dead husband, with the registers we have defective as a mere human testimony — no objection is of much weight, and answers can only be suppositions. But these last are quite sufficient; because, when a contradiction has to be proved, a case possible by supposition shews absolutely there is no contradiction.

There is no proof that Caleb was the son of Hezron, son of Pharez; if it was the same Caleb as in Numbers, he was the son of Jephunneh. One thing is certain, the Hezron in question died in Canaan in Caleb Ephratah, and it was after this that Abiah bore a son. Hence we see there were no early names in Chronicles with "jah"; Abijah was the grandson of one who died in Canaan. In general the names are after the Exodus. Carmi and Hur are given as sons of Judah because they were directly descended from him, for they were clearly not his sons, nor was Shobal; verse 50 shows that Shobal was at least great-grandson of Judah's grandson, and Reaiah was his son, i.e., there were at least six generations.

Similar examples we encounter regularly in the genealogies in the Chronicles. These books run till the time of the return out of captivity and were written in Zechariah’s days. (See e.g. Hur, who after five generations is called the son of Judah in 1 Chr. 4:1).

Jacob begins the action by reciting to Joseph the divine grant of the land of Canaan. This was a setting forth of the family estate, the property which he had to leave among his children. He then adopts the sons of Joseph; for this was needed to the investing of them with the rights of children, inasmuch, as, in a great legal sense, they were strangers to Abraham. Their mother was an Egyptian. They were a seed, therefore, whom the law would, in its day, have put away. Ezra 10:3. But Jacob adopts them. He takes them into the family. "And now," says he to Joseph, "thy two sons, Ephraim and Manasseh, which were born unto thee in the land of Egypt before I came unto thee into Egypt, are mine." They are constituted of the seed of Abraham, and made children of Jacob; and this being done, Jacob at once sets them in the place of the firstborn; for he adds immediately, "As Reuben and Simeon, they shall be mine."

But if there is blessing on the ground of promise secured to Jacob's seed, then Jacob can claim a blessing for Joseph's sons. Jacob can say, "they shall be mine." He claims them as his seed and therefore as the heirs to the inheritance (verses 5, 6).

In Gen. 48 which follows, we get that one act in his life which is signalized by the Spirit as the act of faith. See Heb. 11:21. But the whole chapter is beautiful. All is grace on God's part, and all is faith in the heart of Jacob. For it is the proper business and duty of faith to accept the decisions of grace, and that is just what grace is doing here. Grace adopts the sons of Joseph, who had no title in the flesh, and takes them into the family of Abraham. Grace gives the place and portion of the firstborn, the double portion, as though they were Reuben and Simeon. Grace sets the younger of them above the elder. And grace gives Joseph, or the adopted firstborn, an earnest of his coming inheritance. To all this Jacob bows and is obedient. In faith he accepts the decisions of grace. Nature may resent this; but Jacob is true to the word of grace committed to him. Joseph was moved when Jacob was setting Ephraim above Manasseh. Jacob feels for him; but he fulfils the word of God committed to him, let nature be surprised or wounded as it may. He does not listen to nature in his son Joseph, as he had listened to it on a like occasion, years and years ago, in his mother Rebecca.*